1. Field of the Invention
The present invention relates generally to the field of orthodontic brackets, as an improved orthodontic self-ligating bracket particularly useful in providing tooth corrective treatment to a patient is provided.
2. Related Art
Patients seeking orthodontic treatment are for the most part primarily concerned with the presence of crooked teeth, primarily in the front area of the mouth. Among the chief complaints are dental crowding, flaring, irregularity in tooth alignment, unpleasing tooth appearance, “gummy” smile, and difficulty in chewing, among other issues.
The unpleasant experiences behind these features, nonetheless, may be the result of discrepancy between the supporting bony structures that house the upper and lower dental arches. How to provide a pleasing smile and a proper chewing function while achieving a long-term detention is the ultimate goal of orthodontic treatment. Trained and experienced in skillful orthodontic technique, the Orthodontist seeks to reach these goals for the dental patient with state of the art results.
One of the primary tools employed by orthodontists is the orthodontic bracket. While many different orthodontic bracket constructs have been described, all are generally designed to achieve at least two basic objectives: to provide for attachment to a tooth, and to hold an orthodontic archwire. Both of these objectives work together to provide an orthodontic bracket that will act like an intermediate by connecting an orthodontic archwire to a tooth.
The attachment of the bracket to a tooth will transmit a force to a tooth when a resilient orthodontic archwire is bent or twisted, and then brought to engage with the bracket. This generated force can then be conveyed to the tooth. This process provides for a mechanical force system that functions to generate a force that is delivered sequentially to the teeth, thus directing teeth to the proper positions by the work of the orthodontist.
The conventional design for an orthodontic bracket permits the engagement of an archwire into an archwire slot by ligation using elastomeric or wire ligatures wrapped around the tie wings of the bracket. Ligatures or some form of fastening means are essential to secure an archwire in the bracket slot to prevent the archwire from being dislodged and thus, maintain the position of the active archwire around the dental arch. In cases where tooth extraction is deemed necessary to resolve dental crowding, the crooked teeth can be aligned and slid by orthodontic guidance along an archwire to the extracted space.
Several problems exist in the use of wire ligation for both the orthodontists and the patient. For example, because the ligature wire can trap food particles, oral hygiene care for the patient must be especially diligent throughout treatment. Also, the clinical operation to untie and retie ligature wires for each adjustment required during treatment is time consuming and tedious. Lastly, because of tooth movement that occurs along the archwire, the ligature wire binding creates resistance, resulting in a kind of friction to the tooth movement along the archwire. Thus, the intended corrective tooth movement by the orthodontic mechanical forces may be jeopardized.
To resolve these problems, passive self-ligating (or so-called frictionless) bracket systems have been developed. A separate second member, named the ligating slide, is constructed and is assembled in a self-ligating bracket system. It is displaced to open or close the archwire slot so as to retreat or retain an archwire, respectively. Meanwhile, the play between the sizes of the bracket slot and the archwire permit the sliding of the tooth along the archwire with less friction and/or resistance. In addition, because the design is without ligature wire, tooth cleansing becomes an easier chore for the patient.
In line with this notion, an immediate challenge becomes how to retain the ligating slide in the bracket while effectively maintaining the function of the slide to shift and maintain itself in the proper position. Foster and others report a construct wherein the traveling of the ligating slide can be guided and housed through the design of channels or slide slots at both sides of the brackets (Forster, US 2008/0113311A1; Bathen and Carrier, U.S. Pat. No. 7,621,743 B2; Damon, U.S. Pat. No. 6,071,118; Pletcher, U.S. Pat. No. 5,322,435; Bryant, U.S. Pat. No. D648,030 S). One bracket design uses the concept of the eccentric rotation of the ligating cover about an axial retaining pin, a third member of the bracket system (Hagelganz et al., U.S. Pat. No. 7,585,171 B2).
The designs for bracket systems are dynamic, that is they function to maintain the slide or the cover in a fixed position as open or closed. Such a design relies on a concrete locking mechanism, termed a resilient retention feature, as part of the bracket system. Generally, these resilient retention features fall into three separate groups. The first group of resilient retention features is one in which the open features appear in the outer front surface of the bracket, by including the mating devices in the outer gingival portion of the bracket body with at least one or more coplanar resilient retention features in the ligating slide (Bathen and Carrier, U.S. Pat. No. 7,621,743 B2; Hagelganz et al., U.S. Pat. No. 7,585,171 B2). The second group of resilient feature structures is one in which the hidden features have a built-in detent means, by including a raised detent projection on the recess of the bracket body and the accompanied spaced-apart circular seats on the underside of the ligating slide (Pletcher, U.S. Pat. No. 5,322,435); or by including a rib, serving as a detent, on the underside of the ligating slide with a complementary groove on the bracket body (Damon, U.S. Pat. No. 6,071,118). The third group of resilient retention features is one in which the hidden features, with a third member such as springs, and that by including a projection on the underside of the ligating slide, deflect one or two leaf springs seated in the slot-shaped recess of the bracket body (Forster, US 2008/0113311 A1); or that include a detent means in between two transverse grooves across the underside of the ligating slide, for seating a bent flat spring fitted within a recess of the bracket body (Damon, U.S. Pat. No. 5,466,151). These locking mechanisms, either with coplanar locking or with detent means in the presence or absence of the spring(s), share common physical properties provided by the ligating slides with a modified configuration.
There exist several drawbacks in these designs. For example, the open features of the locking mechanism contain the mating and the resilient retention features, that present the problem of fostering the accumulation of food debris in the areas of the locking features. Appropriate oral hygiene is difficult to maintain, and becomes a constant concern because of this lodging of food particles. Also, since the locking features with relief area built in the position overlay the archwire slot, these features may constantly encounter the increasing mechanical forces delivered by the sequential archwires, and because of this, become weaker with time. Moreover, during treatment, and when the changing of a new archwire is needed, the operator will displace the ligating slide to the (archwire slot) open position for removal of the existing archwire. Due to the improper design of securing the ligating slide in the open position, the operator may notice that the ligating slide may somehow be pushed back by the lip movement. This renders the insertion of the new archwire unfeasible. It is annoying for the operator to repeat the opening of the ligating slide. Another concern is the slipping of the ligating slide off the bracket in the self-ligating bracket system during clinic operation.
Multiple separate members in self-ligating bracket systems can be found in the group with hidden features with a detent system, and a spring which becomes a third member of the bracket. For the spring to function efficiently, it requires proper length of the spring to be seated in the slot-shaped recess of the bracket body. To accommodate this spring feature, accordingly, the labial projection of the overall bracket assembly has to be increased. This leads to an increase in the bracket thickness. Under such circumstance, a minimum thickness of the ligation slide has to be planned to house a complimentary detent and groove/recess feature in the underside. This design may assure the open and the closure of the archwire slot. However, the thickness of the bracket may disturb a patient's lip, especially when canines are in the ectopic positions. In cases where the spring feature is not considered, the resilient retention feature will have to be built in the ligating slide, the drawbacks of which were mentioned previously. Moreover, the ligation slide with its minimum thickness may gradually become strained and distorted when encountering heavier forces delivered sequentially by heavy archwires. In fact, in the clinical setting, the distorted ligation slide makes the slide opening difficult.
Self-locking or self-ligating (ligatureless) orthodontic brackets have been designed. However, most of these have complex designs, incorporating features requiring prohibitively expensive machining operations or comprising multiple separate parts, which in turn increases the number of failure modes for such brackets. Other designs have been rejected in the marketplace due to poor quality or poor design, a lack of available features, difficulty of use, or other factors.
What is needed, therefore, is an improved orthodontic bracket that incorporates a self-ligating capability and that offers a different style of bracket than those available today. Improved orthodontic brackets will also enable the orthodontic professional to more efficiently achieve the most beneficial orthodontic treatment for the patient, while at the same time reducing the various uncomfortable and unpleasant consequences to the patient noted with other types of orthodontic brackets.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.